RESUMEN
Electronic circuits composed of one or more elements with inherent memory, that is, memristors, memcapacitors, and meminductors, offer lower circuit complexity and enhanced functionality for certain computational tasks. Networks of these elements are proposed for novel computational paradigms that rely on information processing and storage on the same physical platform. We show a nanoscaled memdevice able to act as an electronic analogue of tipping buckets that allows reducing the dimensionality and complexity of a sensing problem by transforming it into a counting problem. The device offers a well adjustable, tunable, and reliable periodic reset that is controlled by the amounts of transferred quantum dot charges per gate voltage sweep. When subjected to periodic voltage sweeps, the quantum dot (bucket) may require up to several sweeps before a rapid full discharge occurs thus displaying period doubling, period tripling, and so on between self-governing reset operations.
RESUMEN
Results obtained by an advanced growth of site-controlled quantum dots (SCQDs) on pre-patterned nanoholes and their integration into both photonic resonators and nanoelectronic memories are summarized. A specific technique has been pursued to improve the optical quality of single SCQDs. Quantum dot (QD) layers have been vertically stacked but spectrally detuned for single SCQD studies. Thereby, the average emission linewidth of single QDs could be reduced from 2.3 meV for SCQDs in a first QD layer close to the etched nanoholes down to 600 microeV in the third InAs QD layer. Accurate SCQD nucleation on large QD distances is maintained by vertical strain induced QD coupling throughout the QD stacks. Record narrow linewidths of individual SCQDs down to approximately 110 microeV have been obtained. Experiments performed on coupled photonic SCQD-resonator devices show an enhancement of spontaneous emission. SCQDs have also been integrated deterministically in high electron mobility heterostructures and flash memory operation at room temperature has been observed.
RESUMEN
Disabling forefoot deformity of rheumatoid origin frequently requires surgical intervention. Twenty-three patients (36 feet) who underwent excision of the metatarsal heads in our unit between 1980 and 1987 were assessed clinically and radiologically (n = 12) and by questionnaire (n = 11) at an average 10.5 years (range: 4 to 15) following surgery. Although the procedure was initially successful at the time of review, the result was classified as unsatisfactory because of restriction of walking ability due to pain in the forefoot area in 56% of patients. Recurrence of the deformity--more frequently involving the great toe--had occurred in 72% of patients, and painful callosities were present in 61%. In the patients examined clinically and radiologically, unsatisfactory results were due mainly to mal-alignment of the great toe and extensor tendon tightness. Hindfoot deformity also significantly contributed to pain in the forefoot area. Diminished arthroplasty space, irregular resection cascade, and development of bony spikes were frequently associated with recurrence and callosities. The result of forefoot arthroplasty deteriorates with time. Failure to maintain a plantigrade great toe, intrinsic weakness, and hindfoot deformity were the main factors contributing to an unsatisfactory result.